Method and absorbent composition for recovering a gaseous component from a gas stream

ABSTRACT

A method and apparatus for recovering a gaseous component from an incoming gas stream is described. The incoming gas stream is contacted with a lean aqueous absorbing medium to absorb at least a portion of the gaseous component from the incoming gas stream to form a lean treated gas stream and a rich aqueous absorbing medium. At least a portion of the gaseous component is desorbed from the rich aqueous absorbing medium at a temperature to form an overhead gas stream and a regenerated aqueous absorbing medium. At least a portion of the overhead gas stream is treated to recover a condensate stream. At least a portion of the condensate stream is used to form a heated stream. At least a portion of the heated stream is recycled back to the desorbing step. Novel absorbing medium compositions to recover carbon dioxide and/or hydrogen sulfide are also described.

PRIORITY

This application claims the benefit of U.S. Patent Application No.60/940,529 filed on 29 May 2007, the entirety of which is incorporatedherein by this reference to it.

FIELD

This specification relates generally to methods and apparatuses forrecovering a gaseous component from an incoming gas stream.

BACKGROUND

The following paragraphs are not an admission that anything discussed inthem is prior art or part of the knowledge of persons skilled in theart.

Government regulations on the release of gaseous pollutants into theenvironment are becoming more stringent. Conventional methods andapparatuses for removing a gaseous pollutant from an incoming gas streamtypically suffer from high energy demands.

INTRODUCTION

The following introduction is intended to introduce the reader to thisspecification but not to define any invention. One or more inventionsmay reside in a combination or sub-combination of the apparatus elementsor method steps described below or in other parts of this document. Theinventor does not waive or disclaim his rights to any invention orinventions disclosed in this specification merely by not describing suchother invention or inventions in the claims.

One aspect of a method for recovering a gaseous component from anincoming gas stream described in the specification comprises the step ofcontacting the incoming gas stream with a lean aqueous absorbing mediumto absorb at least a portion of the gaseous component from the incominggas stream to form a lean treated gas stream and a rich aqueousabsorbing medium. The method further comprises the step of desorbing atleast a portion of the gaseous component from the rich aqueous absorbingmedium at a temperature to form an overhead gas stream and a regeneratedaqueous absorbing medium. The method further comprises the step oftreating at least a portion of the overhead gas stream to recover afirst condensate stream. The method further comprises the step of usingat least a portion of the first condensate stream to form a heatedstream. The method further includes the step of recycling at least aportion of the heated stream back to the desorbing step.

In one aspect, heat is transferred from the incoming gas stream to theheated stream.

In another aspect, heat is transferred from the overhead gas stream tothe heated stream.

In yet another aspect, the method further comprises the steps ofintroducing steam to provide heat for the desorbing step and to form asteam condensate and flashing the steam condensate to form a flashedsteam and wherein heat is transferred from the flashed steam to theheated stream.

In a further aspect, heat is transferred from the regenerated aqueousabsorbing medium to the heated stream.

In one aspect, the heated stream comprises the first condensate stream.

In another aspect, the heated stream comprises the rich aqueousabsorbing medium derived by delivering at least a portion of the firstcondensate stream to the contacting step so that at least a portion ofthe first condensate stream combines with the lean aqueous absorbingmedium to form the rich aqueous absorbing medium.

In yet another aspect, the method further comprises the step of treatingat least a portion of the lean treated gas stream to recover a secondcondensate stream and wherein the heated stream comprises a mixedcondensate stream derived by combining at least a portion of the firstcondensate stream with at least a portion of the second condensatestream to form the mixed condensate stream.

In one aspect, the heated stream comprises a rich vapor stream and asemi-lean aqueous absorbing medium derived by delivering at least aportion of the first condensate stream to the contacting step so that atleast a portion of the first condensate stream combines with the leanaqueous absorbing medium to form the rich aqueous absorbing medium whichis subsequently flashed to form the rich vapor stream and the semi-leanaqueous absorbing medium.

In another aspect, heat is transferred from the incoming gas stream toat least one of the rich aqueous absorbing medium or the semi-leanaqueous absorbing medium.

In yet another aspect, heat is transferred from the overhead gas streamto at least one of the rich aqueous absorbing medium or the semi-leanaqueous absorbing medium.

In a further aspect, the method further comprises the steps ofintroducing steam to provide heat for the desorbing step and to form asteam condensate and flashing the steam condensate to form a flashedsteam and wherein heat is transferred from the flashed steam to at leastone of the rich aqueous absorbing medium or the semi-lean aqueousabsorbing medium.

In yet a further aspect, heat is transferred from the regeneratedaqueous absorbing medium to at least one of the rich aqueous absorbingmedium or the semi-lean aqueous absorbing medium.

In one aspect, the heated stream comprises a first rich aqueousabsorbing medium portion and a second rich aqueous absorbing mediumportion derived by delivering at least a portion of the first condensatestream to the contacting step so that at least a portion of the firstcondensate stream combines with the lean aqueous absorbing medium toform the rich aqueous absorbing medium which is subsequently split intothe first rich aqueous medium portion and the second rich aqueousabsorbing medium portion.

In another aspect, heat is transferred from the incoming gas stream toat least one of the rich aqueous absorbing medium, the first richaqueous absorbing medium portion or the second rich absorbing mediumportion.

In yet another aspect, heat is transferred from the overhead gas streamto at least one of the rich aqueous absorbing medium, the first richaqueous absorbing medium portion or the second rich absorbing mediumportion.

In a further aspect, the method further comprises the steps ofintroducing steam to provide heat for the desorbing step and to form asteam condensate and flashing the steam condensate to form a flashedsteam and wherein heat is transferred from the flashed steam to at leastone of the rich aqueous absorbing medium, the first rich aqueousabsorbing medium portion or the second rich absorbing medium portion.

In yet a further aspect, heat is transferred from the regeneratedaqueous absorbing medium to at least one of the rich aqueous absorbingmedium, the first rich aqueous absorbing medium portion or the secondrich absorbing medium portion.

In one aspect, the method further comprises the step of treating atleast a portion of the lean treated gas stream to recover a secondcondensate stream and wherein the heated stream comprises a first mixedcondensate stream portion and a second mixed condensate stream portionderived by combining at least a portion of the first condensate streamwith at least a portion of the second condensate stream to form themixed condensate stream and subsequently splitting the mixed condensatestream to form the first mixed condensate stream portion and the secondmixed condensate stream portion.

In another aspect, heat is transferred from the incoming gas stream toat least one of the mixed condensate stream, the first mixed condensatestream portion or the second mixed condensate stream portion.

In yet another aspect, heat is transferred from the overhead gas streamto at least one of the mixed condensate stream, the first mixedcondensate stream portion or the second mixed condensate stream portion.

In a further aspect, the method further comprises the steps ofintroducing steam to provide heat for the desorbing step and to form asteam condensate and flashing the steam condensate to form a flashedsteam and wherein heat is transferred from the flashed steam to at leastone of the mixed condensate stream, the first mixed condensate streamportion or the second mixed condensate stream portion.

In yet a further aspect, heat is transferred from the regeneratedaqueous absorbing medium to at least one of the mixed condensate stream,the first mixed condensate stream portion or the second mixed condensatestream portion.

In one aspect, the method further comprises the step of recycling theregenerated aqueous absorbing medium back to the contacting step.

In another aspect, the incoming gas stream is a combustion exhaust gas.

In yet another aspect, the gaseous component is carbon dioxide.

In a further embodiment, the lean aqueous absorbing medium comprisesmonoethanolamine, methyldiethanolamine and a suitable solvent.

In yet a further embodiment, the molar ratio of monoethanolamine tomethydiethanolamine is between about 1.5:1 to about 4:1 and the totalmolarity of monoethanolamine and methyldiethanolamine is between about 3moles/liter to about 9 moles/liter.

In one aspect, the molar ratio of monoethanolamine tomethydiethanolamine is about 2.5:1 and the total molarity ofmonoethanolamine and methyldiethanolamine is about 7 moles/liter.

One aspect of an aqueous absorbing medium for removing a gaseouscomponent from an incoming gas stream described in the specificationcomprises monoethanolamine, methyldiethanolamine and a suitable solvent.

In another aspect, the molar ratio of monoethanolamine tomethydiethanolamine is between about 1.5:1 to about 4:1 and the totalmolarity of monoethanolamine and methyldiethanolamine is between about 3moles/liter to about 9 moles/liter.

In yet another aspect, the molar ratio of monoethanolamine tomethydiethanolamine is about 2.5:1 and the total molarity ofmonoethanolamine and methydiethanolamine is about 7 moles/liter.

One aspect of a method for producing an aqueous absorbing mediumdescribed in the specification comprises the steps of providingmonoethanolamine, methyldiethanolamine and a suitable solvent. Themethod further comprises the steps of combining the monoethanolamine,the methyldiethanolamine and the solvent to form the aqueous absorbingmedium.

In another aspect, the molar ratio of monoethanolamine tomethydiethanolamine is between about 1.5:1 to about 4:1 and the totalmolarity of monoethanolamine and methydiethanolamine is between about 3moles/liter to about 9 moles/liter.

In yet another aspect, the molar ratio of monoethanolamine tomethydiethanolamine is about 2.5:1 and the total molarity ofmonoethanolamine and methydiethanolamine is about 7 moles/liter.

One aspect of a method for removing a gaseous component from an incominggas stream described in the specification comprises the step ofcontacting the incoming gas stream with an aqueous absorbing mediumcomprising monoethanolamine, methyldiethanolamine and a suitablesolvent.

In another aspect, the molar ratio of monoethanolamine tomethydiethanolamine is between about 1.5:1 to about 4:1 and the totalmolarity of monoethanolamine and methyldiethanolamine is between about 3moles/liter to about 9 moles/liter.

In yet another aspect, the molar ratio of monoethanolamine tomethydiethanolamine is about 2.5:1 and the total molarity ofmonoethanolamine and methyldiethanolamine is about 7 moles/liter.

Additional features, advantages, and embodiments of one or moreinventions may be set forth or apparent from consideration of thefollowing detailed description, drawings and claims. Moreover, it is tobe understood that both the foregoing introduction and the followingdetailed description provide examples or further explanation withoutlimiting the scope of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a prior art apparatus for recovering a gaseous component froman incoming gas stream;

FIG. 2 is an apparatus for recovering a gaseous component from anincoming gas stream according to a first embodiment described in thespecification;

FIG. 3 is an apparatus for recovering a gaseous component from anincoming gas stream according to a second embodiment described in thespecification;

FIG. 4 is an apparatus for recovering a gaseous component from anincoming gas stream according to a third embodiment described in thespecification;

FIG. 5 is an apparatus for recovering a gaseous component from anincoming gas stream according to a fourth embodiment described in thespecification;

FIG. 6 is an apparatus for recovering a gaseous component from anincoming gas stream according to a fifth embodiment described in thespecification;

FIG. 7 is an apparatus for recovering a gaseous component from anincoming gas stream according to a sixth embodiment described in thespecification;

FIG. 8 is an apparatus for recovering a gaseous component from anincoming gas stream according to a seventh embodiment described in thespecification;

FIG. 9 is an apparatus for recovering a gaseous component from anincoming gas stream according to an eighth embodiment described in thespecification;

FIG. 10 is an apparatus for recovering a gaseous component from anincoming gas stream according to a ninth embodiment described in thespecification;

FIG. 11 is an apparatus for recovering a gaseous component from anincoming gas stream according to a tenth embodiment described in thespecification;

FIG. 12 is an apparatus for recovering a gaseous component from anincoming gas stream according to an eleventh embodiment described in thespecification;

FIG. 13 is an apparatus for recovering a gaseous component from anincoming gas stream according to a twelfth embodiment described in thespecification;

FIG. 14 is an apparatus for recovering a gaseous component from anincoming gas stream according to a thirteenth embodiment described inthe specification;

FIG. 15 is an apparatus for recovering a gaseous component from anincoming gas stream according to a fourteenth embodiment described inthe specification;

FIG. 16 is an apparatus for recovering a gaseous component from anincoming gas stream according to a fifteenth embodiment described in thespecification;

FIG. 17 is an apparatus for recovering a gaseous component from anincoming gas stream according to a sixteenth embodiment described in thespecification;

FIG. 18 is an apparatus for recovering a gaseous component from anincoming gas stream according to a seventeenth embodiment described inthe specification;

FIG. 19 is an apparatus for recovering a gaseous component from anincoming gas stream according to an eighteenth embodiment described inthe specification;

FIG. 20 is an apparatus for recovering a gaseous component from anincoming gas stream according to an nineteenth embodiment described inthe specification;

FIG. 21 is an apparatus for recovering a gaseous component from anincoming gas stream according to a twentieth embodiment described in thespecification;

FIG. 22 is an apparatus for recovering a gaseous component from anincoming gas stream according to a twenty-first embodiment described inthe specification;

FIG. 23 is an apparatus for recovering a gaseous component from anincoming gas stream according to a twenty-second embodiment described inthe specification;

FIG. 24 is an apparatus for recovering a gaseous component from anincoming gas stream according to a twenty-third embodiment described inthe specification;

FIG. 25 is an apparatus for recovering a gaseous component from anincoming gas stream according to a twenty-fourth embodiment described inthe specification; and

FIG. 26 is an apparatus for recovering a gaseous component from anincoming gas stream according to a twenty-fifth embodiment described inthe specification.

DETAILED DESCRIPTION

Various apparatuses or methods will be described below to provide anexample of an embodiment of each claimed invention. No embodimentdescribed below limits any claimed invention and any claimed inventionmay cover apparatuses or methods that are not described below. Theclaimed inventions are not limited to apparatuses or methods having allof the features of any one apparatus or method described below or tofeatures common to multiple or all of the apparatuses described below.It is possible that an apparatus or method described below is not anembodiment of any claimed invention. The applicants, inventors andowners reserve all rights in any invention disclosed in an apparatus ormethod described below that is not claimed in this document and do notabandon, disclaim or dedicate to the public any such invention by itsdisclosure in this document.

FIG. 1 shows a prior art apparatus 100 for recovering carbon dioxidefrom an incoming gas stream. A carbon dioxide laden incoming gas streamin line 112 is fed to a gas-liquid contact apparatus 114 where it iscontacted with a lean aqueous absorbing medium fed to the contactapparatus 114 by line 116. Carbon dioxide is absorbed from the incominggas stream 112 to form a lean treated gas stream that exits the contactapparatus 114 by line 118. A rich aqueous absorbing medium containingdissolved carbon dioxide is removed from the contact apparatus 114 byline 138 with pump 140. The rich aqueous absorbing medium 138 can beheated in a cross heat exchanger 142 against a regenerated lean aqueousabsorbing medium and is subsequently fed to a regenerator 144 by line146. The regenerator 144 is operated at a temperature with heat providedfrom a steam reboiler 148 so that the carbon dioxide is desorbed fromthe rich aqueous absorbing medium to form an overhead gas stream thatexits the regenerator 144 by line 150. A regenerated aqueous absorbingmedium is removed from the regenerator 144 by line 164. The overhead gasstream 150 passes through a condenser 152 fed by cooling water 154 tocondense liquid from the overhead gas stream 150. An overhead gas streamcontaining the condensed liquid in line 156 is delivered to a flash drum158 to separate a carbon dioxide rich product gas stream in line 160from a condensate stream in line 162. The condensate stream in line 162is recycled back to the regenerator 144.

Still referring to FIG. 1, heat from the steam reboiler 148 is used tooperate the regenerator 144 at a relatively high temperature rangingfrom between about 80° C. to about 160° C. However, the condensatestream 162 is at a temperature between about 30° C. to about 40° C. Theintroduction of this relatively cool condensate stream 162 back into theregenerator 144 lowers the operating temperature of the regenerator 144.Accordingly, additional heat is required to raise the temperature backup to the optimal operating range to efficiently desorb carbon dioxidefrom the rich aqueous absorbing medium.

In one aspect of a method described in the specification, the inventorshave attempted to reduce the heat duty of the regenerator (i.e. theamount of the external steam required to operate the regenerator).Accordingly, unlike in the conventional apparatus and method describedabove, at least a portion of the condensate stream recovered from theoverhead gas stream is used to form a heated stream that is subsequentlyrecycled back to the regenerator. In one aspect, heat already containedwithin the apparatus is transferred to the heated stream before beingrecycled back to the regenerator.

For consistency, the apparatuses and methods described in detail belowin FIGS. 2-26 make reference to the recovery of carbon dioxide (CO₂)from an incoming gas stream. However, it is understood that theapparatuses and methods described in detail below can also be used torecover other types of gaseous components from incoming gas streams,including, but not limited to, hydrogen sulfide (H₂S), sulfur dioxide(SO₂), chlorine (Cl₂), and ammonia (NH₃). Furthermore, the specificaqueous absorbing medium compositions described in detail below can beused for the recovery of carbon dioxide and/or hydrogen sulfide.

It is to be appreciated that the source, composition, and otherparameters of the incoming gas may vary considerably and will depend onthe particular source. The types of incoming gas streams that can betreated, can include, but are not limited to, flue gas streams frompower plants such as coal-fired power plants, natural gas combinedcycles, natural gas boilers, natural gas, gas streams from gasificationplants, gas from cement manufacturing, reformate gas, synthesis gas,refinery off-gas, biogas and air (e.g., in a space application). Ifrequired, the incoming gas stream can be pretreated prior to enteringthe apparatus (e.g., fractionation, filtration, scrubbing to removeparticulates and other gaseous components, and combination or dilutionwith other gases). Accordingly, the chemical composition may also varyconsiderably. Suitable incoming gas streams typically contain betweenabout 0.03 to about 80% by volume carbon dioxide, specifically betweenabout 1 to about 33% by volume carbon dioxide, and more specificallybetween about 3 to about 15% by volume carbon dioxide.

With respect to the gas-liquid contact apparatus, it is understood thatthe particular type of absorber will depend in part on the specificcomposition, flow rate, pressure and/or temperature of the incoming gasstream. However, any form of absorber may be employed consistent withthe aim of efficiently removing carbon dioxide from the incoming gasstream and being absorbed into the aqueous absorbing medium. Theabsorber is essentially a counter-current column with a circular orrectangular cross-section, and with a suitable height andcross-sectional area sufficient to effect the removal of carbon dioxideto a specified clean-up target. The column internals could be in theform of structured or random packing providing adequate number of stagesto meet the clean-up target, or plates (valve, sieve, or bubble cap)with an adequate number of plates to meet the clean-up target. The topof the absorber column can also include a demister or off-gas scrubbersection which is used for the purpose of recovering the absorbing mediumentrained in water vapors from the absorber section and to cool theoff-gas at a temperature to help maintain a water balance across theplant. The absorber column itself can contain a number of sections eachseparated by a chimney tray that allows gas to pass up through to thenext section but ensures liquid separation to entrain water dropletsfrom the exiting lean gas.

With respect to the regenerator, any type of stripper may be employedconsistent with the aim of efficiently desorbing at least a portion ofthe carbon dioxide from the rich aqueous absorbing medium. The stripperis typically a column with a circular cross-section, and with a suitableheight and cross-sectional area sufficient to effect the stripping ofcarbon dioxide to provide a lean absorbing medium using an externallysupplied source of heat. For example, a reboiler can be connected to thebottom part of the stripping column to provide the heat supply in theform of steam. The column internals can be in the form of structured orrandom packing providing an adequate number of stages to meet thestripping function, or plates (valve, sieve or bubble cap) with numberof plates to meet the same stripping function.

FIG. 2 shows an apparatus 200 for recovering carbon dioxide from anincoming gas stream according to a first embodiment described in thespecification. In this embodiment, the heated stream comprises thecondensate stream recovered from the overhead gas stream. In thisembodiment, heat from the incoming gas stream, the regenerated aqueousabsorbing medium, and the overhead gas stream is transferred to theheated stream before being recycled back to the regenerator. However, itis to be appreciated that it is sufficient to transfer heat from atleast one of the streams in the apparatus to the heated stream beforebeing recycled back to the regenerator.

A carbon dioxide laden incoming gas stream in line 212 can be cooled ina heat exchanger 203 against the condensate stream recovered from theoverhead gas stream which will be described in more detail below.Moreover, if required, the incoming gas stream can be fed to a cooler204 to further reduce the temperature of the incoming gas stream to anacceptable level and can be subsequently fed to a flash drum 205 toremove excess moisture in line 206 before entering a gas-liquid contactapparatus 214. The cooled incoming gas stream is fed to the gas-liquidcontact apparatus 214 where it is contacted with a lean aqueousabsorbing medium fed to the contact apparatus 214 by line 216. Carbondioxide is absorbed from the incoming gas stream to form a lean treatedgas stream that exits the contact apparatus 214 by line 218. The leantreated gas stream 218 passes through a cooler 220 fed by cooling water222 to condense liquid from the lean treated gas stream 218. A leantreated gas stream containing the condensed liquid in line 224 isdelivered to a flash drum 226 to separate a water-depleted lean treatedgas stream in line 228 from a condensate stream in line 230. Thecondensate stream in line 230 is ultimately recycled back to the contactapparatus 214 via pump 234. The water-depleted lean treated gas streamin line 228 may be processed further, if desired, before venting via achimney, flare stack, or the like.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 214 by line 238 with pump 240. Therich aqueous absorbing medium can be heated in a cross heat exchanger242 against a regenerated lean aqueous absorbing medium and issubsequently fed to a regenerator 244 by line 246. The regenerator 244is operated at a temperature with heat provided from a steam reboiler248 so that the carbon dioxide is desorbed from the rich aqueousabsorbing medium to form an overhead gas stream that exits theregenerator 244 by line 250. The overhead gas stream 250 is cooled in aheat exchanger 202 and is subsequently fed to a condenser 252. Thecondenser 252 is fed by cooling water 254 to condense liquid from theoverhead gas stream 250. An overhead gas stream containing the condensedliquid in line 256 is delivered to a flash drum 258 to separate a carbondioxide rich product gas stream in line 260 from a condensate stream inline 262. The condensate stream in line 262 is removed with pump 263 andis delivered to a heat exchanger 201 where it is heated against theregenerated lean aqueous absorbing medium. The condensate stream isdelivered to a heat exchanger 202 where it is heated against theoverhead gas stream in line 250. The condensate stream is delivered to aheat exchanger 203 where it is heated against the incoming gas stream inline 212 and is subsequently recycled back to the regenerator 244.

A regenerated lean aqueous absorbing medium is removed from theregenerator 244 in line 264 and is fed to the steam reboiler 248. Steamis fed to the steam reboiler in line 266 and is removed in the form of asteam condensate in line 268. Heat from the steam is transferred to theregenerated lean aqueous absorbing medium to form a vapor stream whichis recycled back to the regenerator 244 in line 270 and a regeneratedlean aqueous absorbing medium which exits the steam reboiler 248 in line272. It is to be appreciated that the regenerated lean aqueous absorbingmedium in line 272 has a lower carbon dioxide loading than theregenerated lean aqueous absorbing medium in line 264. The regeneratedlean aqueous absorbing medium is delivered to heat exchanger 242 by line272 where it is cooled by the rich aqueous absorbing medium in line 238.The regenerated lean aqueous absorbing medium is delivered to heatexchanger 201 where it is cooled by the condensate stream in line 262.If required, the regenerated aqueous absorbing medium in line 274 can bedelivered to a cooler 276 fed by cooling water 278 to reduce thetemperature of the regenerated aqueous absorbing medium to a level thatis acceptable for the contact apparatus 214. The regenerated aqueousabsorbing medium is removed from the cooler 276 in line 280 by pump 236and is mixed with the condensate stream in 230. The regenerated aqueousabsorbing medium is ultimately recycled back to the contact apparatus214 in line 216.

FIGS. 3-7 show apparatuses for recovering carbon dioxide from anincoming gas stream according to further embodiments described in thespecification. In these embodiments, the heated stream comprises therich aqueous absorbing medium derived by delivering at least a portionof the condensate stream recovered from the overhead gas stream to thecontact apparatus so that at least a portion of the condensate streamcombines with the lean aqueous absorbing medium to form the rich aqueousabsorbing medium. As will be explained in more detail below, heat fromat least one of the incoming gas stream, the overhead gas stream, theregenerated aqueous absorbing medium, or flashed steam derived fromflashing a steam condensate can be transferred to the heated streambefore being delivered to the regenerator.

FIG. 3 shows an apparatus 300 for recovering carbon dioxide from anincoming gas stream according to a second embodiment described in thespecification. A carbon dioxide laden incoming gas stream in line 312 isfed to a gas-liquid contact apparatus 314 where it is contacted with alean aqueous absorbing medium fed to the contact apparatus 314 by line316. If required, the incoming gas stream can be pretreated (not shown)to reduce the temperature and remove excess moisture before entering thecontact apparatus 314. Carbon dioxide is absorbed from the incoming gasstream 312 to form a lean treated gas stream that exits the contactapparatus 314 by line 318. The lean treated gas stream 318 passesthrough a cooler 320 fed by cooling water 322 to condense liquid fromthe lean treated gas stream 318. A lean treated gas stream containingthe condensed liquid in line 324 is delivered to a flash drum 326 toseparate a water-depleted lean treated gas stream in line 328 from acondensate stream in line 330. The condensate stream in line 330 isdelivered to a mixer 332 with pump 334 and is ultimately recycled backto the contact apparatus 314 with pump 336 in line 316. Thewater-depleted lean treated gas stream in line 328 may be processedfurther, if desired, before venting via a chimney, flare stack, or thelike.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 314 by line 338 with pump 340. Therich aqueous absorbing medium 338 is heated in a cross heat exchanger342 against a regenerated aqueous absorbing medium and is subsequentlyfed to a regenerator 344 by line 346. The regenerator 344 is operated ata temperature with heat provided from a steam reboiler 348 so that thecarbon dioxide is desorbed from the rich aqueous absorbing medium toform an overhead gas stream that exits the regenerator 344 by line 350.The overhead gas stream 350 passes through a condenser 352 fed bycooling water 354 to condense liquid from the overhead gas stream 350.An overhead gas stream containing the condensed liquid in line 356 isdelivered to a flash drum 358 to separate a carbon dioxide rich productgas stream in line 360 from a condensate stream in line 362. Thecondensate stream 362 is delivered to a mixer 332 and is ultimately fedto the contact apparatus 314 with pump 336 in line 316. At least aportion of the condensate stream recovered from the overhead gas streamin line 362 combines with the lean aqueous absorbing medium and fed tothe contact apparatus 314 to form the rich aqueous absorbing medium.

A regenerated lean aqueous absorbing medium is removed from theregenerator 344 in line 364 and is fed to the steam reboiler 348. Steamis fed to the steam reboiler in line 366 and is removed in the form of asteam condensate in line 368. Heat from the steam is transferred to theregenerated lean aqueous absorbing medium to form a vapor stream whichis recycled back to the regenerator 348 in line 370 and a regeneratedlean aqueous absorbing medium which exits the steam reboiler 348 in line372. The regenerated lean aqueous absorbing medium is delivered to heatexchanger 342 by line 372 where it is cooled by the rich aqueousabsorbing medium in line 338. If required, the regenerated aqueousabsorbing medium in line 374 can be delivered to a cooler 376 fed bycooling water 378 to reduce the temperature of the regenerated aqueousabsorbing medium to a level that is acceptable for the contact apparatus314. The regenerated aqueous absorbing medium is removed from the cooler376 in line 380 and is delivered to a mixer 332 where it is mixed withthe condensate stream in line 330 and the condensate stream in line 362.The regenerated aqueous absorbing medium is ultimately recycled back tothe contact apparatus 314 in line 316.

FIG. 4 shows an apparatus 400 for recovering carbon dioxide from anincoming gas stream according to a third embodiment described in thespecification. The third embodiment is the same as the secondembodiment, except as described in detail below.

In this embodiment, there are two additional heat exchangers 401, 402 totransfer more heat to the rich aqueous absorbing medium before enteringthe regenerator.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 414 by line 438 with pump 440. Therich aqueous absorbing medium is delivered to a heat exchanger 401 whereit is heated against the regenerated lean aqueous absorbing medium. Therich aqueous absorbing medium is delivered to a heat exchanger 402 whereit is heated against the overhead gas stream in line 450. The richaqueous absorbing medium is delivered to a heat exchanger 442 where itis further heated against the regenerated aqueous lean absorbing mediumand is subsequently fed into the regenerator 444 by line 446.

FIG. 5 shows an apparatus 500 for recovering carbon dioxide from anincoming gas stream according to a fourth embodiment described in thespecification. The fourth embodiment is the same as the thirdembodiment, except as described in detail below.

In the fourth embodiment, there is an additional heat exchanger 503 totransfer more heat to the rich aqueous absorbing medium before enteringthe regenerator. If required, the apparatus can also include a cooler504 to further cool down the incoming gas stream and a flash drum 505 toseparate out the excess moisture in line 506 from the incoming gasstream before entering the contact apparatus 514.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 514 by line 538 with pump 540. Therich aqueous absorbing medium 538 is delivered to a heat exchanger 501where it is heated against the regenerated lean aqueous absorbingmedium. The rich aqueous absorbing medium is delivered to a heatexchanger 503 where it is heated against the incoming gas stream. Therich aqueous absorbing medium is delivered to a heat exchanger 502 whereit is heated against the overhead gas stream. The rich aqueous absorbingmedium is delivered to a heat exchanger 542 where it is further heatedagainst the regenerated aqueous lean absorbing medium and issubsequently fed into the regenerator 544 by line 546.

FIG. 6 shows an apparatus 600 for recovering carbon dioxide from anincoming gas stream according to a fifth embodiment described in thespecification. The fifth embodiment is the same as the third embodiment,except as described in detail below.

In this embodiment, there is an additional heat exchanger 607 totransfer more heat to the rich aqueous absorbing medium before enteringthe regenerator and a flash drum 608 for flashing the steam condensateexiting the reboiler to form a flashed steam.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 614 by line 638 with pump 640. Therich aqueous absorbing medium is delivered to a heat exchanger 601 whereit is heated against the regenerated lean aqueous absorbing medium. Therich aqueous absorbing medium is delivered to a heat exchanger 602 whereit is heated against the overhead gas stream. Steam condensate isremoved from the steam reboiler 648 in line 668 and is fed to a flashdrum 608 that separates the flashed steam in line 609 from the flashedsteam condensate in line 610. The rich aqueous absorbing medium isdelivered to a heat exchanger 607 where it is further heated against theflashed steam in line 609. The rich aqueous absorbing medium isdelivered to a heat exchanger 642 where it is further heated against theregenerated lean aqueous absorbing medium and is subsequently fed intothe regenerator 644 by line 646.

FIG. 7 shows an apparatus 700 for recovering carbon dioxide from anincoming gas stream according to a sixth embodiment described in thespecification. The sixth embodiment is the same as the fifth embodiment,except as described in detail below.

In this embodiment, there is an additional heat exchanger 711 totransfer more heat to the rich aqueous absorbing medium before enteringthe regenerator, the regenerated lean aqueous absorbing medium is splitinto two portions 772A, 772B, and there is an additional heat exchanger703 to transfer more heat to a portion of the regenerated lean aqueousabsorbing medium 772A before entering the regenerator. In essence, theheat exchanger 703 acts as an additional reboiler supplementing theexisting steam reboiler 748. If required, the apparatus can also includea cooler 704 to further cool down the incoming gas stream and a flashdrum 705 to separate out the excess moisture in line 706 from theincoming gas stream before entering the contact apparatus 714.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 714 by line 738 with pump 740. Therich aqueous absorbing medium is delivered to a heat exchanger 711 whereit is heated against the incoming gas stream. The rich aqueous absorbingmedium is delivered to a heat exchanger 701 where it is heated against aportion of the regenerated lean aqueous absorbing medium 772B. The richaqueous absorbing medium is delivered to a heat exchanger 702 where itis heated against the overhead gas stream. Steam condensate is removedfrom the steam reboiler 748 in line 768 and is fed to a flash drum 708that separates the flashed steam in line 709 from the flashed steamcondensate in line 710. The rich aqueous absorbing medium is deliveredto a heat exchanger 707 where it is further heated against the flashedsteam in line 709. The rich aqueous absorbing medium is delivered to aheat exchanger 742 where it is further heated against a portion of theregenerated lean aqueous absorbing medium 772B and is subsequently fedinto the regenerator 744 by line 746.

A regenerated lean aqueous absorbing medium is removed from theregenerator 744 in line 764 and is fed to the steam reboiler 748. Steamis fed to the steam reboiler in line 766 and is removed in the form of asteam condensate in line 768. Heat from the steam is transferred to theregenerated lean aqueous absorbing medium to form a vapor stream whichis recycled back to the regenerator 748 in line 770 and a regeneratedlean aqueous absorbing medium which exits the steam reboiler 748 in line772. The regenerated lean aqueous absorbing medium is split into twoportions 772A, 772B. The portion of regenerated lean aqueous absorbingmedium 772A is delivered to a heat exchanger 703 where it is heatedagainst the incoming gas stream and is subsequently fed into theregenerator 748. The portion of the regenerated lean aqueous absorbingmedium 772B is delivered to a heat exchanger 742 where it is cooled bythe rich aqueous absorbing medium. The portion of regenerated aqueousabsorbing medium 772B is delivered to a heat exchanger 701 where it isfurther cooled by the rich aqueous absorbing medium. If required, theportion of regenerated aqueous absorbing medium 772B can be delivered toa cooler 776 fed by cooling water 778 to reduce the temperature of theregenerated aqueous absorbing medium to a level that is acceptable forthe contact apparatus 714. The regenerated aqueous absorbing medium isremoved from the cooler 776 and is delivered to a mixer 732 where it ismixed with the condensate stream in line 730 and the condensate stream762. The portion of the regenerated aqueous absorbing medium 772B isultimately recycled back to the contact apparatus 714 in line 716.

FIG. 8 shows an apparatus 800 for recovering carbon dioxide from anincoming gas stream according to a seventh embodiment described in thespecification. The seventh embodiment is the same as the fifthembodiment, except as described in detail below.

In this embodiment, the heated stream comprises a rich vapor stream anda semi-lean aqueous absorbing medium derived by delivering at least aportion of the condensate stream recovered from the overhead gas streamto the contacting apparatus so that at least a portion of the condensatestream combines with the lean aqueous absorbing medium to form the richaqueous absorbing medium which is subsequently flashed to form the richvapor stream and the semi-lean aqueous absorbing medium. In thisembodiment, heat from the regenerated aqueous absorbing medium, theoverhead gas stream and flashed steam derived from flashing a steamcondensate is transferred to the rich aqueous absorbing medium beforebeing flashed to form the rich vapor stream and the semi-lean aqueousabsorbing medium. Additionally, heat from the regenerated aqueousabsorbing medium is transferred to the semi-lean absorbing medium beforeentering the regenerator.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 814 by line 838 with pump 840. Therich aqueous absorbing medium is delivered to a heat exchanger 801 whereit is heated against the regenerated lean aqueous absorbing medium. Therich aqueous absorbing medium is delivered to a heat exchanger 802 whereit is heated against the overhead gas stream. Steam condensate isremoved from the steam reboiler 848 in line 868 and is fed to a flashdrum 808 that separates the flashed steam in line 809 from the flashedsteam condensate in line 810. The rich aqueous absorbing medium isdelivered to a heat exchanger 807 where it is further heated against theflashed steam in line 809. The rich aqueous absorbing medium isdelivered to a flash drum 813 where it is separated into a rich vaporstream which is fed back into the regenerator 844 in line 815 and asemi-lean aqueous absorbing medium that is delivered to a heat exchanger842 in line 817 where it is heated against the regenerated lean aqueousabsorbing medium and is subsequently fed back to the regenerator 844.

FIGS. 9-12 show apparatuses for recovering carbon dioxide from anincoming gas stream according to further embodiments described in thespecification. In these embodiments, the heated stream comprises a firstrich aqueous absorbing medium portion and a second rich aqueousabsorbing medium portion derived by delivering at least a portion of thecondensate stream recovered from the overhead gas stream to the contactapparatus so that at least a portion of the condensate stream combineswith the lean aqueous absorbing medium to form the rich aqueousabsorbing medium which is subsequently split into the first rich aqueousmedium portion and the second rich aqueous absorbing medium portion. Aswill be explained in more detail below, heat from at least one of theincoming gas stream, the overhead gas stream, the regenerated aqueousabsorbing medium, or flashed steam derived from flashing a steamcondensate is transferred to at least one of the rich aqueous absorbingmedium before being split into two portions, the first rich aqueousabsorbing medium portion or the second rich aqueous medium portionbefore being delivered to the regenerator.

FIG. 9 shows an apparatus 900 for recovering carbon dioxide from anincoming gas stream according to an eighth embodiment described in thespecification. The eighth embodiment is the same as the thirdembodiment, except as described in detail below.

In this embodiment, the rich aqueous absorbing medium is splitimmediately downstream of heat exchanger 901 into two portions 938A,938B.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 914 by line 938 with pump 940. Therich aqueous absorbing medium is delivered to a heat exchanger 901 whereit is heated against the regenerated lean aqueous absorbing medium. Therich aqueous absorbing medium is then split into two portions 938A,938B. In one aspect, about 74% by volume can be diverted to portion 938Aand about 26% by volume can be diverted to portion 938B. The portion ofrich aqueous absorbing medium 938A is delivered to a heat exchanger 942where it is further heated against the regenerated aqueous leanabsorbing medium and is subsequently fed into the regenerator 944. Theportion of the rich aqueous absorbing medium 938B is delivered to a heatexchanger 902 where it is heated against the overhead gas stream and issubsequently fed into the regenerator 944.

FIG. 10 shows an apparatus 1000 for recovering carbon dioxide from anincoming gas stream according to a ninth embodiment described in thespecification. The ninth embodiment is the same as the eighthembodiment, except as described in detail below.

In this embodiment, there is an additional heat exchanger 1007 totransfer more heat to a portion of the rich aqueous absorbing medium1038B before entering the regenerator and a flash drum 1008 to formflashed steam from the steam condensate exiting the reboiler.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 1014 by line 1038 with pump 1040. Therich aqueous absorbing medium is delivered to a heat exchanger 1001where it is heated against the regenerated lean aqueous absorbingmedium. The rich aqueous absorbing medium is then split into twoportions 1038A, 1038B. In one aspect, about 73% by volume can bediverted to portion 1038A and about 27% by volume can be diverted toportion 1038B. The portion of rich aqueous absorbing medium 1038A isdelivered to a heat exchanger 1042 where it is further heated againstthe regenerated aqueous lean absorbing medium and is subsequently fedinto the regenerator 1044. The portion of the rich aqueous absorbingmedium 1038B is delivered to a heat exchanger 1002 where it is heatedagainst the overhead gas stream. Steam condensate is removed from thesteam reboiler 1048 in line 1068 and is fed to a flash drum 1008 thatseparates the flashed steam in line 1009 from the flashed steamcondensate in line 1010. The portion of the rich aqueous absorbingmedium 1038B is delivered to a heat exchanger 1007 where it is furtherheated against the flashed steam in line 1009 and is subsequently fedinto the regenerator 1044.

FIG. 11 shows an apparatus 1100 for recovering carbon dioxide from anincoming gas stream according to a tenth embodiment described in thespecification. The tenth embodiment is the same as the secondembodiment, except as described in detail below.

In this embodiment, the rich aqueous absorbing medium 1138 is splitimmediately downstream of the pump 1140 into two portions 1138A, 1138Band there are two additional heat exchangers 1102, 1103 to transfer moreheat to the portion of the rich aqueous absorbing medium 1138B beforeentering the regenerator. If required, the apparatus 1100 can alsoinclude a cooler 1104 to further cool down the incoming gas stream and aflash drum 1105 to separate out the excess moisture in line 1106 fromthe incoming gas stream before entering the contact apparatus 1114.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 1114 by line 1138 with pump 1140. Therich aqueous absorbing medium is then split into two portions 1138A,1138B. In one aspect, about 78% by volume can be diverted to portion1138A and about 22% by volume can be diverted to portion 1138B. Theportion of rich aqueous absorbing medium 1138A is delivered to a heatexchanger 1142 where it is heated against the regenerated lean aqueousabsorbing medium and is subsequently fed to the regenerator 1144. Theportion of the rich aqueous absorbing medium 1138B is delivered to aheat exchanger 1103 where it is heated against the incoming gas stream.The portion of the rich aqueous absorbing medium 1138B is delivered to aheat exchanger 1102 where it is heated against the overhead gas streamand is subsequently fed to the regenerator 1144.

FIG. 12 shows an apparatus 1200 for recovering carbon dioxide from anincoming gas stream according to a eleventh embodiment described in thespecification. The eleventh embodiment is the same as the tenthembodiment, except as described in detail below.

In this embodiment, there is an additional heat exchanger 1207 totransfer more heat to the portion of the rich aqueous absorbing medium1238B before entering the regenerator and a flash drum 1208 to formflashed steam from the steam condensate exiting the reboiler.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 1214 by line 1238 with pump 1240. Therich aqueous absorbing medium is then split into two portions 1238A,1238B. In one aspect, about 79% by volume can be diverted to portion1238A and about 21% by volume can be diverted to portion 1238B. Theportion of rich aqueous absorbing medium 1238A is delivered to a heatexchanger 1242 where it is heated against the regenerated lean aqueousabsorbing medium and is subsequently fed to the regenerator 1244. Theportion of the rich aqueous absorbing medium 1238B is delivered to aheat exchanger 1203 where it is heated against the incoming gas stream.The portion of the rich aqueous absorbing medium 1138B is delivered to aheat exchanger 1202 where it is heated against the overhead gas stream.Steam condensate is removed from the steam reboiler 1248 in line 1268and is fed to a flash drum 1208 that separates the flashed steam in line1209 from the flashed steam condensate in line 1210. The portion of therich aqueous absorbing medium 1238B is delivered to a heat exchanger1207 where it is further heated against the flashed steam in line 1209and is subsequently fed into the regenerator 1244.

FIGS. 13-17 show apparatuses for recovering carbon dioxide from anincoming gas stream according to further embodiments described in thespecification. In these embodiments, the heated stream comprises a mixedcondensate stream derived by combining at least a portion of thecondensate stream recovered from the overhead gas stream with at least aportion of the condensate stream recovered from the lean treated gasstream to form the mixed condensate stream. As will be explained in moredetail below, heat from at least one of the incoming gas stream, theoverhead gas stream, the regenerated aqueous absorbing medium, andflashed steam derived from flashing a steam condensate is transferred tothe heated stream before being recycled back to the regenerator.

FIG. 13 shows an apparatus 1300 for recovering carbon dioxide from anincoming gas stream according to a twelfth embodiment described in thespecification.

A carbon dioxide laden incoming gas stream in line 1312 is fed to agas-liquid contact apparatus 1314 where it is contacted with a leanaqueous absorbing medium fed to the contact apparatus 1314 by line 1316.If required, the incoming gas stream can be pretreated to reduce thetemperature and remove excess moisture before entering the contactapparatus 1314. Carbon dioxide is absorbed from the incoming gas stream1312 to form a lean treated gas stream that exits the contact apparatus1314 by line 1318. The lean treated gas stream 1318 passes through acooler 1320 fed by cooling water 1322 to condense liquid from the leantreated gas stream 1318. A lean treated gas stream containing thecondensed liquid in line 1324 is delivered to a flash drum 1326 toseparate a water-depleted lean treated gas stream in line 1328 from acondensate stream in line 1330. The condensate stream in line 1330 isdelivered to a mixer 1332 with pump 1334 and is mixed with a condensatestream recovered from the overhead gas stream to form a mixed condensatestream as will be described in more detail below.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 1314 by line 1338 with pump 1340. Therich aqueous absorbing medium 1338 is heated in a cross heat exchanger1342 against a regenerated aqueous absorbing medium and is subsequentlyfed to a regenerator 1344 by line 1346. The regenerator 1344 is operatedat a temperature with heat provided from a steam reboiler 1348 so thatthe carbon dioxide is desorbed from the rich aqueous absorbing medium toform an overhead gas stream that exits the regenerator 1344 by line1350. The overhead gas stream is cooled in a heat exchanger 1302 againstthe mixed condensate stream. The overhead gas stream passes through acondenser 1352 fed by cooling water 1354 to condense liquid from theoverhead gas stream. An overhead gas stream containing the condensedliquid in line 1356 is delivered to a flash drum 1358 to separate acarbon dioxide rich product gas stream in line 1360 from a condensatestream in line 1362. The condensate stream 1362 is delivered to a mixer1332 where it is mixed with condensate stream 1330 to form the mixedcondensate stream in line 1319.

The mixed condensate stream in line 1319 is delivered to a heatexchanger 1301 where it is heated against the regenerated lean aqueousabsorbing medium. The mixed condensate stream is delivered to a heatexchanger 1302 where it is heated against the overhead gas stream. Atleast a portion of the mixed condensate stream is recycled back to theregenerator 1344 in a vapor stream 1370 as will be described in moredetail below.

A regenerated lean aqueous absorbing medium is removed from theregenerator 1344 in line 1364 and can be sent to a mixer 1321 where itcan be mixed with the mixed condensate stream to form a supplementedmixed condensate stream 1323 before being fed into the steam reboiler1348. Steam is fed to the steam reboiler in line 1366 and is removed inthe form of a steam condensate in line 1368. Heat from the steam istransferred to the supplemented mixed condensate stream 1323 to form avapor stream which is recycled back to the regenerator 1344 in line 1370and a regenerated lean aqueous absorbing medium which exits the steamreboiler 1348 in line 1372. At least a portion of the mixed condensatestream enters the vapor stream 1370 and is recycled back into theregenerator 1344. The regenerated lean aqueous absorbing medium isdelivered to heat exchanger 1342 by line 1372 where it is cooled by therich aqueous absorbing medium in line 1338. The regenerated lean aqueousabsorbing medium is delivered to a heat exchanger 1301 where it isfurther cooled by the mixed condensate stream. If required, theregenerated aqueous absorbing medium in line 1374 can be delivered to acooler 1376 fed by cooling water 1378 to reduce the temperature of theregenerated aqueous absorbing medium to a level that is acceptable forthe contact apparatus 1314. The regenerated aqueous absorbing medium isremoved from the cooler 1376 in line 1380 and is ultimately recycledback to the contact apparatus 1314 in line 1316 with pump 1336.

FIG. 14 shows an apparatus 1400 for recovering carbon dioxide from anincoming gas stream according to a thirteenth embodiment described inthe specification.

A carbon dioxide laden incoming gas stream in line 1412 can be cooled ina heat exchanger 1403 against a mixed condensate stream which will bedescribed in more detail below. If required, the incoming gas stream canbe fed to a cooler 1404 to further reduce the temperature to anacceptable level and can be subsequently fed to a flash drum 1405 toremove excess moisture in line 1406 before entering a gas-liquid contactapparatus 1414. The cooled incoming gas stream is fed to a gas-liquidcontact apparatus 1414 where it is contacted with a lean aqueousabsorbing medium fed to the contact apparatus 1414 by line 1416. Carbondioxide is absorbed from the incoming gas stream 1412 to form a leantreated gas stream that exits the contact apparatus 1414 by line 1418.The lean treated gas stream 1418 passes through a cooler 1420 fed bycooling water 1422 to condense liquid from the lean treated gas stream1418. A lean treated gas stream containing the condensed liquid in line1424 is delivered to a flash drum 1426 to separate a water-depleted leantreated gas stream in line 1428 from a condensate stream in line 1430.The condensate stream in line 1430 is delivered to a mixer 1432 withpump 1434 and is mixed with a condensate stream recovered from theoverhead gas stream as will be described in more detail below.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 1414 by line 1438 with pump 1440. Therich aqueous absorbing medium is delivered to a heat exchanger 1401where it is heated against the regenerated lean aqueous absorbingmedium. The rich aqueous absorbing medium is delivered to a heatexchanger 1402 where it is heated against the overhead gas stream. Therich aqueous absorbing medium is delivered to a heat exchanger 1442where it is further heated against the regenerated aqueous leanabsorbing medium and is subsequently fed into the regenerator 1444 byline 1446. The regenerator 1444 is operated at a temperature with heatprovided from a steam reboiler 1448 so that the carbon dioxide isdesorbed from the rich aqueous absorbing medium to form an overhead gasstream that exits the regenerator 1444 by line 1450. The overhead gasstream is cooled in a heat exchanger 1402 against the rich aqueousabsorbing medium. The overhead gas stream passes through a condenser1452 fed by cooling water 1454 to condense liquid from the overhead gasstream. An overhead gas stream containing the condensed liquid in line1456 is delivered to a flash drum 1458 to separate a carbon dioxide richproduct gas stream in line 1460 from a condensate stream in line 1462.The condensate stream 1462 is delivered to a mixer 1432 where it ismixed with condensate stream 1430 to form a mixed condensate stream.

The mixed condensate stream in line 1419 is delivered to a heatexchanger 1403 where it is heated against the incoming gas stream. Atleast a portion of the mixed condensate stream is recycled back to theregenerator 1444 in a vapor stream 1470 as will be described in moredetail below.

A regenerated lean aqueous absorbing medium is removed from theregenerator 1444 in line 1464 and can be sent to a mixer 1421 where itcan be mixed with the mixed condensate stream to form a supplementedmixed condensate stream 1423 before being fed into the steam reboiler1448. Steam is fed to the steam reboiler in line 1466 and is removed inthe form of a steam condensate in line 1468. Heat from the steam istransferred to the supplemented mixed condensate stream 1423 to form avapor stream which is recycled back to the regenerator 1444 in line 1470and a regenerated lean aqueous absorbing medium which exits the steamreboiler 1448 in line 1472. At least a portion of the mixed condensatestream enters the vapor stream 1470 and is recycled back into theregenerator 1444. The regenerated lean aqueous absorbing medium isdelivered to heat exchanger 1442 by line 1472 where it is cooled by therich aqueous absorbing medium in line 1438. The regenerated lean aqueousabsorbing medium is delivered to heat exchanger 1401 where it is furthercooled by the rich aqueous absorbing medium. The regenerated aqueousabsorbing medium in line 1474 is delivered to a cooler 1476 fed bycooling water 1478 to reduce the temperature of the regenerated aqueousabsorbing medium to a level that is acceptable for the contact apparatus1414. The regenerated aqueous absorbing medium is removed from thecooler 1476 in line 1480 is ultimately recycled back to the contactapparatus 1414 in line 1416 with pump 1436.

FIG. 15 shows an apparatus 1500 for recovering carbon dioxide from anincoming gas stream according to a fourteenth embodiment described inthe specification. The fourteenth embodiment is the same as thethirteenth embodiment, except as described below.

In this embodiment, there is an additional heat exchanger 1507 totransfer more heat to the mixed condensate stream before entering theregenerator and a flash drum 1508 to form flashed steam 1509 from thesteam condensate 1568 exiting the steam reboiler 1548.

The mixed condensate stream in line 1519 is delivered to a heatexchanger 1503 where it is heated against the incoming gas stream. Steamcondensate is removed from the steam reboiler 1548 in line 1568 and isfed to a flash drum 1508 that separates the flashed steam in line 1509from the flashed steam condensate in line 1510. The mixed condensatestream is delivered to a heat exchanger 1507 where it is further heatedagainst the flashed steam in line 1509. At least a portion of the mixedcondensate stream is recycled back to the regenerator 1544 in a vaporstream 1570 as will be described in more detail below.

A regenerated lean aqueous absorbing medium is removed from theregenerator 1544 in line 1564 and can be sent to a mixer 1521 where itcan be mixed with the mixed condensate stream to form a supplementedmixed condensate stream 1523 before being fed into the steam reboiler1548. Steam is fed to the steam reboiler in line 1566 and is removed inthe form of a steam condensate in line 1568. Heat from the steam istransferred to the supplemented mixed condensate stream 1523 to form avapor stream which is recycled back to the regenerator 1544 in line 1570and a regenerated lean aqueous absorbing medium which exits the steamreboiler 1548 in line 1572. At least a portion of the mixed condensatestream enters the vapor stream 1570 and is recycled back into theregenerator 1544.

FIG. 16 shows an apparatus 1600 for recovering carbon dioxide from anincoming gas stream according to a fifteenth embodiment described in thespecification. The fifteenth embodiment is the same as the fourteenthembodiment, except as described below.

In this embodiment, the rich aqueous absorbing medium is splitimmediately downstream of heat exchanger 1601 into two portions 1638A,1638B.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 1614 by line 1638 with pump 1640. Therich aqueous absorbing medium is delivered to a heat exchanger 1601where it is heated against the regenerated lean aqueous absorbingmedium. The rich aqueous absorbing medium is then split into twoportions 1638A, 1638B. The portion of rich aqueous absorbing medium1638A is delivered to a heat exchanger 1642 where it is further heatedagainst the regenerated aqueous lean absorbing medium and issubsequently fed into the regenerator 1644. The portion of the richaqueous absorbing medium 1638B is delivered to a heat exchanger 1602where it is heated against the overhead gas stream and is subsequentlyfed into the regenerator 1644.

FIG. 17 shows an apparatus 1700 for recovering carbon dioxide from anincoming gas stream according to a sixteenth embodiment described in thespecification.

A carbon dioxide laden incoming gas stream in line 1712 can be cooled ina heat exchanger 1703 against a mixed condensate stream which will bedescribed in more detail below. If required, the incoming gas stream canbe fed to a cooler 1704 to further reduce the temperature to anacceptable level and can be subsequently fed to a flash drum 1705 toremove excess moisture in line 1706 before entering a gas-liquid contactapparatus 1714. The cooled incoming gas stream is fed to a gas-liquidcontact apparatus 1714 where it is contacted with a lean aqueousabsorbing medium fed to the contact apparatus 1714 by line 1716. Carbondioxide is absorbed from the incoming gas stream 1712 to form a leantreated gas stream that exits the contact apparatus 1714 by line 1718.The lean treated gas stream 1718 passes through a cooler 1720 fed bycooling water 1722 to condense liquid from the lean treated gas stream1718. A lean treated gas stream containing the condensed liquid in line1724 is delivered to a flash drum 1726 to separate a water-depleted leantreated gas stream in line 1728 from a condensate stream in line 1730.The condensate stream in line 1730 is delivered to a mixer 1732 withpump 1734 and is mixed with a condensate stream recovered from theoverhead gas stream as will be described in more detail below.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 1714 by line 1738 with pump 1740. Therich aqueous absorbing medium is delivered to a heat exchanger 1701where it is heated against the regenerated lean aqueous absorbingmedium. The rich aqueous absorbing medium is then split into twoportions 1738A, 1738B. The portion of rich aqueous absorbing medium1738A is delivered to a heat exchanger 1742 where it is further heatedagainst the regenerated aqueous lean absorbing medium and issubsequently fed into the regenerator 1744. The portion of the richaqueous absorbing medium 1738B is delivered to a heat exchanger 1702where it is heated against the overhead gas stream. Steam condensate isremoved from the steam reboiler 1748 in line 1768 and is fed to a flashdrum 1708 that separates the flashed steam in line 1709 from the flashedsteam condensate in line 1710. The portion of the rich aqueous absorbingmedium 1738B is delivered to a heat exchanger 1707 where it is furtherheated against the flashed steam in line 1709 and is subsequently fedinto the regenerator 1744. The regenerator 1744 is operated at atemperature with heat provided from a steam reboiler 1748 so that thecarbon dioxide is desorbed from the rich aqueous absorbing medium toform an overhead gas stream that exits the regenerator 1744 by line1750. The overhead gas stream is cooled in a heat exchanger 1702 againstthe rich aqueous absorbing medium. The overhead gas stream passesthrough a condenser 1752 fed by cooling water 1754 to condense liquidfrom the overhead gas stream. An overhead gas stream containing thecondensed liquid in line 1756 is delivered to a flash drum 1758 toseparate a carbon dioxide rich product gas stream in line 1760 from acondensate stream in line 1762. The condensate stream 1762 is deliveredto a mixer 1732 where it is mixed with condensate stream 1730 to form amixed condensate stream.

The mixed condensate stream in line 1719 is delivered to a heatexchanger 1703 where it is heated against the incoming gas stream and issubsequently fed to the regenerator 1744.

A regenerated lean aqueous absorbing medium is removed from theregenerator 1744 in line 1764 and is fed to the steam reboiler 1748.Steam is fed to the steam reboiler in line 1766 and is removed in theform of a steam condensate in line 1768. Heat from the steam istransferred to the regenerated lean aqueous absorbing medium to form avapor stream which is recycled back to the regenerator 1744 in line 1770and a regenerated lean aqueous absorbing medium which exits the steamreboiler 1748 in line 1772. The regenerated lean aqueous absorbingmedium is delivered to heat exchanger 1742 by line 1772 where it iscooled by the portion of the rich aqueous absorbing medium in line1738A. If required, the regenerated lean aqueous absorbing medium can bedelivered to heat exchanger 1701 where it is further cooled by the richaqueous absorbing medium. The regenerated aqueous absorbing medium inline 1774 is delivered to a cooler 1776 fed by cooling water 1778 toreduce the temperature of the regenerated aqueous absorbing medium to alevel that is acceptable for the contact apparatus 1714. The regeneratedaqueous absorbing medium is removed from the cooler 1776 in line 1780 isultimately recycled back to the contact apparatus 1714 in line 1716 withpump 1736.

FIGS. 18-24 show apparatuses for recovering carbon dioxide from anincoming gas stream according to further embodiments described in thespecification. In these embodiments, the heated stream comprises a firstmixed condensate stream portion and a second mixed condensate streamportion derived by combining at least a portion of a condensate streamrecovered from an overhead gas stream with at least a portion of thecondensate stream recovered from the lean treated gas stream to form themixed condensate stream and subsequently splitting the mixed condensatestream to form the first mixed condensate stream portion and the secondmixed condensate stream portion. As will be explained in more detailbelow, heat from at least one of the incoming gas stream, the overheadgas stream, the regenerated aqueous absorbing medium, or flashed steamderived from a flashing a steam condensate is transferred to at leastone of the mixed condensate stream before being split into two portions,the first mixed condensate stream portion or the second mixed condensatestream portion before being recycled back to the regenerator.

FIG. 18 shows an apparatus 1800 for recovering carbon dioxide from anincoming gas stream according to a seventeenth embodiment described inthe specification.

A carbon dioxide laden incoming gas stream in line 1812 can be cooled ina heat exchanger 1803 against a portion of a mixed condensate stream1819A which will be described in more detail below. If required, theincoming gas stream can be fed to a cooler 1804 to further reduce thetemperature to an acceptable level and can be subsequently fed to aflash drum 1805 to remove excess moisture in line 1806 before entering agas-liquid contact apparatus 1814. The cooled incoming gas stream is fedto a gas-liquid contact apparatus 1814 where it is contacted with a leanaqueous absorbing medium fed to the contact apparatus 1814 by line 1816.Carbon dioxide is absorbed from the incoming gas stream 1812 to form alean treated gas stream that exits the contact apparatus 1814 by line1818. The lean treated gas stream 1818 passes through a cooler 1820 fedby cooling water 1822 to condense liquid from the lean treated gasstream 1818. A lean treated gas stream containing the condensed liquidin line 1824 is delivered to a flash drum 1826 to separate awater-depleted lean treated gas stream in line 1828 from a condensatestream in line 1830. The condensate stream in line 1830 is delivered toa mixer 1832 with pump 1834 and is mixed with a condensate streamrecovered from the overhead gas stream as will be described in moredetail below.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 1814 by line 1838 with pump 1840. Therich aqueous absorbing medium is delivered to a heat exchanger 1802where it is heated against the overhead gas stream. The rich aqueousabsorbing medium is delivered to a heat exchanger 1842 where it isfurther heated against the regenerated aqueous lean absorbing medium andis subsequently fed into the regenerator 1844 by line 1846. Theregenerator 1844 is operated at a temperature with heat provided from asteam reboiler 1848 so that the carbon dioxide is desorbed from the richaqueous absorbing medium to form an overhead gas stream that exits theregenerator 1844 by line 1850. The overhead gas stream is cooled in aheat exchanger 1802 against the rich aqueous absorbing medium. Theoverhead gas stream passes through a condenser 1852 fed by cooling water1854 to condense liquid from the overhead gas stream. An overhead gasstream containing the condensed liquid in line 1856 is delivered to aflash drum 1858 to separate a carbon dioxide rich product gas stream inline 1860 from a condensate stream in line 1862. The condensate stream1862 is delivered to a mixer 1832 where it is mixed with condensatestream 1830 to form a mixed condensate stream.

The mixed condensate stream in line 1819 is delivered to a heatexchanger 1801 where it is heated against the regenerated lean aqueousabsorbing medium. The mixed condensate stream is split into two streams1819A and 1819B. In one aspect, about 23% by volume can be diverted toportion 1819A and about 77% by volume can be diverted to portion 1819B.The portion of the mixed condensate stream 1819A is delivered to a heatexchanger 1803 where it is heated against the incoming gas and issubsequently fed to the regenerator 1844. Steam condensate is removedfrom the steam reboiler 1848 in line 1868 and is fed to a flash drum1808 that separates the flashed steam in line 1809 from the flashedsteam condensate in line 1810. The portion of mixed condensate stream1819B is delivered to a heat exchanger 1807 where it is further heatedagainst the flashed steam in line 1809. At least a portion of the mixedcondensate stream is recycled back to the regenerator 1844 in a vaporstream 1870 as will be described in more detail below.

A regenerated lean aqueous absorbing medium is removed from theregenerator 1844 in line 1864 and can be sent to a mixer 1821 where itcan be mixed with the portion of the mixed condensate stream 1819B toform a supplemented mixed condensate stream 1823 before being fed intothe steam reboiler 1848. Steam is fed to the steam reboiler in line 1866and is removed in the form of a steam condensate in line 1868. Heat fromthe steam is transferred to the supplemented mixed condensate stream1823 to form a vapor stream which is recycled back to the regenerator1844 in line 1870 and a regenerated lean aqueous absorbing medium whichexits the steam reboiler 1848 in line 1872. At least a portion of themixed condensate stream 1819B enters the vapor stream 1870 and isrecycled back into the regenerator 1844. The regenerated lean aqueousabsorbing medium is delivered to heat exchanger 1842 by line 1872 whereit is cooled by the rich aqueous absorbing medium in line 1838. Theregenerated lean aqueous absorbing medium is delivered to heat exchanger1801 where it is further cooled by the mixed condensate stream 1819. Ifrequired, the regenerated aqueous absorbing medium in line 1874 can bedelivered to a cooler 1876 fed by cooling water 1878 to reduce thetemperature of the regenerated aqueous absorbing medium to a level thatis acceptable for the contact apparatus 1814. The regenerated aqueousabsorbing medium is removed from the cooler 1876 in line 1880 and isultimately recycled back to the contact apparatus 1814 in line 1816 withpump 1836.

FIG. 19 shows an apparatus 1900 for recovering carbon dioxide from anincoming gas stream according to a eighteenth embodiment described inthe specification.

A carbon dioxide laden incoming gas stream in line 1912 can be cooled ina heat exchanger 1903 against a portion of a mixed condensate stream1919A which will be described in more detail below. If required, theincoming gas stream can be fed to a cooler 1904 to further reduce thetemperature to an acceptable level and can be subsequently fed to aflash drum 1905 to remove excess moisture in line 1906 before entering agas-liquid contact apparatus 1914. The cooled incoming gas stream is fedto a gas-liquid contact apparatus 1914 where it is contacted with a leanaqueous absorbing medium fed to the contact apparatus 1914 by line 1916.Carbon dioxide is absorbed from the incoming gas stream 1912 to form alean treated gas stream that exits the contact apparatus 1914 by line1918. The lean treated gas stream 1918 passes through a cooler 1920 fedby cooling water 1922 to condense liquid from the lean treated gasstream 1918. A lean treated gas stream containing the condensed liquidin line 1924 is delivered to a flash drum 1926 to separate awater-depleted lean treated gas stream in line 1928 from a condensatestream in line 1930. The condensate stream in line 1930 is delivered toa mixer 1932 with pump 1934 and is mixed with a condensate streamrecovered from the overhead gas stream as will be described in moredetail below.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 1914 by line 1938 with pump 1940. Therich aqueous absorbing medium is delivered to a heat exchanger 1942where it is heated against the regenerated aqueous lean absorbing mediumand is subsequently fed into the regenerator 1944 by line 1946. Theregenerator 1944 is operated at a temperature with heat provided from asteam reboiler 1948 so that the carbon dioxide is desorbed from the richaqueous absorbing medium to form an overhead gas stream that exits theregenerator 1944 by line 1950. The overhead gas stream is cooled in aheat exchanger 1902 against the mixed condensate stream. The overheadgas stream passes through a condenser 1952 fed by cooling water 1954 tocondense liquid from the overhead gas stream. An overhead gas streamcontaining the condensed liquid in line 1956 is delivered to a flashdrum 1958 to separate a carbon dioxide rich product gas stream in line1960 from a condensate stream in line 1962. The condensate stream 1962is delivered to a mixer 1932 where it is mixed with condensate stream1930 to form a mixed condensate stream.

The mixed condensate stream in line 1919 is delivered to a heatexchanger 1901 where it is heated against the regenerated lean aqueousabsorbing medium. The mixed condensate stream is delivered to a heatexchanger 1902 where it is heated against the overhead gas stream. Themixed condensate stream is split into two streams 1919A and 1919B. Inone aspect, about 82.5% by volume can be diverted to portion 1919A andabout 17.5% by volume can be diverted to portion 1919B. The portion ofthe mixed condensate stream 1919A is delivered to a heat exchanger 1903where it is heated against the incoming gas. At least a portion of themixed condensate stream 1919A is recycled back to the regenerator 1944in a vapor stream 1970 as will be described in more detail below. Steamcondensate is removed from the steam reboiler 1948 in line 1968 and isfed to a flash drum 1908 that separates the flashed steam in line 1909from the flashed steam condensate in line 1910. The portion of mixedcondensate stream 1919B is delivered to a heat exchanger 1907 where itis further heated against the flashed steam in line 1909. At least aportion of the mixed condensate stream 1919B is recycled back to theregenerator 1944 in a vapor stream 1970 as will be described in moredetail below.

A regenerated lean aqueous absorbing medium is removed from theregenerator 1944 in line 1964 and can be sent to a mixer 1921 where itcan be mixed with the portion of the mixed condensate stream 1919A andthe portion of the mixed condensate stream 1919B to form a supplementedmixed condensate stream 1923 before being fed into the steam reboiler1948. Steam is fed to the steam reboiler in line 1966 and is removed inthe form of a steam condensate in line 1968. Heat from the steam istransferred to the supplemented mixed condensate stream 1923 to form avapor stream which is recycled back to the regenerator 1944 in line 1970and a regenerated lean aqueous absorbing medium which exits the steamreboiler 1948 in line 1972. At least a portion of the mixed condensatestreams 1919A, 1919B enters the vapor stream 1970 and is recycled backinto the regenerator 1944. The regenerated lean aqueous absorbing mediumis delivered to heat exchanger 1942 by line 1972 where it is cooled bythe rich aqueous absorbing medium in line 1938. The regenerated leanaqueous absorbing medium is delivered to heat exchanger 1901 where it isfurther cooled by the mixed condensate stream 1919. If required, theregenerated aqueous absorbing medium in line 1974 can be delivered to acooler 1976 fed by cooling water 1978 to reduce the temperature of theregenerated aqueous absorbing medium to a level that is acceptable forthe contact apparatus 1914. The regenerated aqueous absorbing medium isremoved from the cooler 1976 in line 1980 and is ultimately recycledback to the contact apparatus 1914 in line 1916 with pump 1936.

FIG. 20 shows an apparatus 2000 for recovering carbon dioxide from anincoming gas stream according to a nineteenth embodiment described inthe specification. The nineteenth embodiment is the same as theeighteenth embodiment, except as described in detail below.

In this embodiment, the portion of the mixed condensate stream 2019Athat exits the heat exchanger 2003 is fed directly back into theregenerator 2044 instead of being fed to the steam reboiler 2048 whereit is sent back into the regenerator 2044 through the vapor stream 2070.

FIG. 21 shows an apparatus 2100 for recovering carbon dioxide from anincoming gas stream according to a twentieth embodiment described in thespecification. The twentieth embodiment is the same as the nineteenthembodiment, except as described in detail below.

In this embodiment, there is an additional heat exchanger 2125 totransfer more heat to the rich aqueous absorbing medium before enteringthe regenerator 2144 and the mixed condensate stream is splitimmediately downstream of heat exchanger 2101 into two portions 2119A,2119B.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 2114 by line 2138 with pump 2140. Therich aqueous absorbing medium is delivered to a heat exchanger 2125where it is heated against the overhead gas stream. The rich aqueousabsorbing medium is delivered to a heat exchanger 2142 where it isheated against the regenerated aqueous lean absorbing medium and issubsequently fed into the regenerator 2144 by line 2146.

The mixed condensate stream in line 2119 is delivered to a heatexchanger 2101 where it is heated against the regenerated lean aqueousabsorbing medium. The mixed condensate stream is split into two streams2119A and 2119B. In one aspect, about 28% by volume can be diverted toportion 2119A and about 72% by volume can be diverted to portion 2119B.The portion of the mixed condensate stream 2119A is delivered to a heatexchanger 2103 where it is heated against the incoming gas and issubsequently fed back into to the regenerator 2144. The portion of themixed condensate stream 2119B is delivered to a heat exchanger 2102where it is heated against the overhead gas stream. Steam condensate isremoved from the steam reboiler 2148 in line 2168 and is fed to a flashdrum 2108 that separates the flashed steam in line 2109 from the flashedsteam condensate in line 2110. The portion of mixed condensate stream2119B is delivered to a heat exchanger 2107 where it is further heatedagainst the flashed steam in line 2109. At least a portion of the mixedcondensate stream 2119B is recycled back to the regenerator 2144 in avapor stream 2170 as previously described above.

FIG. 22 shows an apparatus 2200 for recovering carbon dioxide from anincoming gas stream according to a twenty-first embodiment described inthe specification. The twenty-first embodiment is the same as thetwentieth embodiment, except as described in detail below.

In this embodiment, the mixed condensate stream is split immediatelydownstream of the mixer 2232 into two portions 2219A, 2219B.

The mixed condensate stream is split into two streams 2219A and 2219B.In one aspect, about 86% by volume can be diverted to portion 2219A andabout 14% by volume can be diverted to portion 2219B. The portion of themixed condensate stream 2219A is delivered to a heat exchanger 2203where it is heated against the incoming gas and is subsequently fed backinto to the regenerator 2244. The portion of the mixed condensate streamin line 2219B is delivered to a heat exchanger 2201 where it is heatedagainst the regenerated lean aqueous absorbing medium. The portion ofthe mixed condensate stream 2219B is delivered to a heat exchanger 2202where it is heated against the overhead gas stream. Steam condensate isremoved from the steam reboiler 2248 in line 2268 and is fed to a flashdrum 2208 that separates the flashed steam in line 2209 from the flashedsteam condensate in line 2210. The portion of mixed condensate stream2219B is delivered to a heat exchanger 2207 where it is further heatedagainst the flashed steam in line 2209. At least a portion of the mixedcondensate stream 2219B is recycled back to the regenerator 2244 in avapor stream 2270 as previously described above.

FIG. 23 shows an apparatus 2300 for recovering carbon dioxide from anincoming gas stream according to a twenty-second embodiment described inthe specification. The twenty-second embodiment is the same as thetwenty-first embodiment, except as described in detail below.

In this embodiment, heat exchanger 2301 is used to transfer heat to therich aqueous absorbing medium instead of to the portion of the mixedcondensate stream 2319B.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 2314 by line 2338 with pump 2340. Therich aqueous absorbing medium is delivered to a heat exchanger 2301where it is heated against the regenerated lean aqueous absorbingmedium. The rich aqueous absorbing medium is delivered to a heatexchanger 2325 where it is heated against the overhead gas stream. Therich aqueous absorbing medium is delivered to a heat exchanger 2342where it is further heated against the regenerated aqueous leanabsorbing medium and is subsequently fed into the regenerator 2344 byline 2346.

The mixed condensate stream is split into two streams 2319A and 2319B.The portion of the mixed condensate stream 2319A is delivered to a heatexchanger 2303 where it is heated against the incoming gas and issubsequently fed back into to the regenerator 2344. The portion of themixed condensate stream 2319B is delivered to a heat exchanger 2302where it is heated against the overhead gas stream. Steam condensate isremoved from the steam reboiler 2348 in line 2368 and is fed to a flashdrum 2308 that separates the flashed steam in line 2309 from the flashedsteam condensate in line 2310. The portion of mixed condensate stream2319B is delivered to a heat exchanger 2307 where it is further heatedagainst the flashed steam in line 2309. At least a portion of the mixedcondensate stream 2319B is recycled back to the regenerator 2344 in avapor stream 2370 as previously described above.

FIG. 24 shows an apparatus 2400 for recovering carbon dioxide from anincoming gas stream according to a twenty-third embodiment described inthe specification. The twenty-third embodiment is the same as thetwenty-second embodiment, except as described in detail below.

In this embodiment, the rich aqueous absorbing medium is splitimmediately downstream of heat exchanger 2401 into two portions 2438A,2438B.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 2414 by line 2438 with pump 2440. Therich aqueous absorbing medium is delivered to a heat exchanger 2401where it is heated against the regenerated lean aqueous absorbingmedium. The rich aqueous absorbing medium is then split into twoportions 2438A, 2438B. In one aspect, about 75% by volume can bediverted to portion 2438A and about 25% by volume can be diverted toportion 2438B. The portion of rich aqueous absorbing medium 2438A isdelivered to a heat exchanger 2442 where it is further heated againstthe regenerated aqueous lean absorbing medium and is subsequently fedinto the regenerator 2444. The portion of the rich aqueous absorbingmedium 2438B is delivered to a heat exchanger 2425 where it is heatedagainst the overhead gas stream and is subsequently fed into theregenerator 2444.

FIG. 25 shows an apparatus 2500 for recovering carbon dioxide from anincoming gas stream according to a twenty-fourth embodiment described inthe specification. The twenty-fourth embodiment is the same as the tenthembodiment, except as described in detail below.

In this embodiment, a reboiler is not used. Instead, a relatively lowpressure steam (e.g., between about 30 to about 103 kPa) can bedelivered directly to the regenerator 2544 as live steam injection 2597.This low pressure steam can be waste steam from another plant (e.g., apower generating plant) or some other low grade source of low pressuresteam (e.g., heat recovery steam generators using hot flue gas, excesssteam from heating plants, waste heat boilers, heat from carbon dioxidecompression, etc.).

The condensate stream recovered from the overhead gas stream 2562, thecondensate stream recovered from the lean treated gas stream 2530 and,if required, the condensate stream recovered from the incoming gasstream 2506 can be mixed 2598 and delivered back to the source of thelow pressure steam (e.g., a boiler system) to maintain a water balance.If required, the condensate streams 2562, 2530, 2506 can be treatedbefore being sent back to the source of the low pressure steam.

FIG. 26 shows an apparatus 2600 for recovering carbon dioxide from anincoming gas stream according to a twenty-fifth embodiment described inthe specification. The twenty-fifth embodiment is the same as theseventh embodiment, except as described in detail below.

In this embodiment, there is an additional heat exchanger 2625 totransfer more heat to the rich aqueous absorbing medium from thestripper overhead gas stream 2650 before being split with 10% of theabsorbing medium stream 2638B to be further heated in the heat exchanger2602 before entering the regenerator 2644. The remaining 90% of the richabsorbing medium of stream 2638A is sent to the heat exchanger 2642where it is heated further by the lean aqueous absorbing medium beforeentering the regenerator 2644. Reflux condensate accumulated in vessel2658 is mixed with the absorber overhead wash water at 2632 where thecombined reflux and the condensed absorber overhead vapors are returnedback to the process to be preheated in heat exchanger 2601 prior toentering heat exchanger 2603. In essence, the heat exchanger 2603 actsas an additional reboiler supplementing the existing steam reboiler2648. If required, the apparatus can also include a cooler 2604 tofurther cool down the incoming gas stream and a flash drum 2605 toseparate out the excess moisture in line 2606 from the incoming gasstream before entering the contact apparatus 2614.

A rich aqueous absorbing medium containing dissolved carbon dioxide isremoved from the contact apparatus 2614 by line 2638 with pump 2640. Therich aqueous absorbing medium is delivered to a heat exchanger 2611where it is heated against the incoming gas stream. The rich aqueousabsorbing medium is then delivered to a heat exchanger 2625 where it isheated against the overhead gas stream 2650. The rich absorbing mediumis then split with 10% of the stream 2638B delivered to a heat exchanger2602 where it is heated against the overhead gas stream before enteringthe apparatus 2644. The remaining stream 2638B is heated against thelean aqueous absorbing medium in heat exchanger 2642 before it isdelivered to the regenerator 2644 by line 2646.

A regenerated lean aqueous absorbing medium is removed from theregenerator 2644 where a portion in line 2623 is fed to the steamreboiler 2648 with the remaining fed to the heat exchanger 2642 by line2672. Steam is fed to the steam reboiler in line 2666 and is removed inthe form of a steam condensate in line 2668. Heat from the steam istransferred to the regenerated lean aqueous absorbing medium to form avapor stream which is recycled back to the regenerator 2644 in line2670. Lean aqueous absorbing medium from heat exchanger 2642 is fed toheat exchanger 2601 where it is further cooled by the process overheadcondensate fed by line 2619. If required, the regenerated aqueousabsorbing medium 2672 is delivered to a cooler 2676 fed by cooling water2678 to reduce the temperature of the regenerated aqueous absorbingmedium to a level that is acceptable for the contact apparatus 2614.

The combined reflux and absorber overhead condensate is preheatedagainst a hot lean aqueous absorbing medium in heat exchanger 2601 byline 2619. The combined condensate is further heated in the flue gasheat exchanger 2603 where it is partially converted to steam vapors. Thestream is then delivered to the regenerator 2644 providing additionalregeneration energy as well as maintaining water balance within theprocess. This ultimately reduces the amount of steam required in thereboiler 2648.

It is to be appreciated that any type of aqueous absorbing medium torecover carbon dioxide and/or hydrogen sulfide from an incoming gasstream that is known in the art can be used in any of the novelapparatuses and methods described in this specification. The aqueousabsorbing mediums can include, but are not limited to, monoethanolaminediethanol amine, triethanol amine, SELEXOL™ (a dimethyl ether ofpolyethylene glycol), di-isopropanol amine, 2-amino-2-methyl-1-propanol,piperazine, and sulfolane.

In a further aspect of the specification, an aqueous absorbing mediumthat can be used to recover carbon dioxide and/or hydrogen sulfide froman incoming gas stream is described in detail below. It is to beappreciated that the aqueous absorbing medium can be used both in theconventional apparatuses and methods know to a person skilled in the artor in any of the novel apparatuses and methods described in thisspecification.

The aqueous absorbing medium comprises monoethanolamine,methyldiethanolamine and a suitable solvent. Solvents that are suitablefor the absorbing medium include those that solubilize themonoethanolamine and methyldiethanolamine and which act as an absorbentfor carbon dioxide or hydrogen sulfide. Examples of suitable solventsinclude, but are not limited to, water, methanol, ethanol, and anycombinations thereof. In one aspect, the molar ratio of monoethanolamineto methydiethanolamine is between about 1.5:1 to about 4:1 and the totalmolarity of monoethanolamine and methyldiethanolamine is between about 3moles/liter to about 9 moles/liter. In yet a further aspect, the molarratio of monoethanolamine to methydiethanolamine is about 2.5:1 and thetotal molarity of monoethanolamine and methyldiethanolamine is about 7moles/liter.

In yet a further aspect of the specification, a method for producing anaqueous absorbing medium that can be used to recover carbon dioxideand/or hydrogen sulfide from an incoming gas stream is described. Themethod comprises the step of providing monoethanolamine,methyldiethanolamine, and a suitable solvent. The method furthercomprises the step of combining the monoethanolamine, themethyldiethanolamine and the solvent to form the aqueous absorbingmedium. In one aspect, the monoethanolamine to methydiethanolamine isprovided in a molar ratio of between about 1.5:1 to about 4:1 and thetotal molarity of monoethanolamine and methydiethanolamine is betweenabout 3 moles/liter to about 9 moles/liter. In yet a further aspect, themolar ratio of monoethanolamine to methydiethanolamine is about 2.5:1and the total molarity of monoethanolamine and methyldiethanolamine isabout 7 moles/liter.

In yet a further aspect, a method for removing a gaseous component froman incoming gas stream is described. The method comprises contacting theincoming gas stream with an aqueous absorbing medium comprisingmonoethanolamine, methyldiethanolamine and a suitable solvent. In oneaspect, the molar ratio of monoethanolamine to methydiethanolamine isbetween about 1.5:1 to about 4:1 and the total molarity ofmonoethanolamine and methyldiethanolamine is between about 3 moles/literto about 9 moles/liter. In yet a further aspect, the molar ratio ofmonoethanolamine to methydiethanolamine is about 2.5:1 and the totalmolarity of monoethanolamine and methyldiethanolamine is about 7moles/liter.

EXAMPLES General Information Relating to Examples 1-32 and 35-38

Data was obtained through a plant experiment and computer simulationsbased on the International Test Center for Carbon Dioxide Capture (ITC)Multi-Purpose Technology Development CO₂ Capture Plant at the Universityof Regina, Regina, Saskatchewan, Canada. The plant is designed toproduce 1 tonne of CO₂ per day from a flue gas obtained from a naturalgas fired boiler. The incoming gas stream had the following compositionon a ‘wet basis’ before any type of processing: 9.574 mole % CO₂, 0.909mol % O₂, 72.285 mol % N₂, and 17.232 mol % H₂O. Furthermore, theincoming gas stream had the following conditions on a ‘wet basis’ beforeany processing: inlet gas pressure 95.36 kPa, inlet gas temperature 150°C., and inlet gas flow 10 kg-mol/hr. The incoming gas stream wasprocessed to lower the temperature and remove excess moisture beforeentering the absorber. The processed incoming gas stream had thefollowing composition: 11.169 mol % CO₂, 1.060 mol % O₂, 84.329 N₂,3.442 H₂O. Furthermore, the processed incoming gas stream had thefollowing conditions: inlet gas pressure 111.325 kPa, inlet gastemperature 36-40° C., inlet gas flow 8.57 kg-mol/hr. In Examples 1-32,the steam supply pressure to the reboiler was between a range of about230-475 kPa, the steam supply temperature to the reboiler was between arange of about 125-150° C., and the reboiler temperature was about 121°C. The absorber efficiency was 90%. The computer simulations wereprepared using PROMAX™ software obtained from Bryan Research &Engineering, Bryan, Tex., USA.

Examples 1-2

Example 1 was an actual plant experiment based on FIG. 1 that shows aprior art apparatus for recovering carbon dioxide from an incoming gasstream. Example 1 used an aqueous absorbing medium with a concentrationof 5 mol/L MEA and a circulation rate of 14 L/min.

Example 2 was a computer simulation based on FIG. 1 that shows a priorart apparatus for recovering carbon dioxide from an incoming gas stream.Example 2 also used an aqueous absorbing medium with a concentration of5 mol/L MEA and a circulation rate of 14 L/min.

In Example 1, the plant experiment resulted in a heat duty of 72,890BTU/(lb-mol of CO₂ produced). In Example 2, the corresponding computersimulation resulted in a heat duty of 70,110 BTU/(lb-mol of CO₂produced). This correlation shows that the computer simulations arecapable of closely predicting the experimental results.

Examples 3-24

Examples 3-24 were computer simulations based on FIGS. 2-16 and 18-24,respectively. Examples 3-24 used an aqueous absorbing medium with aconcentration of 5 mol/L MEA and a circulation rate of 14 L/min.

Examples 25-32

Examples 25-32 were computer simulations based on FIGS. 1, 2, 9, 12, 17,22, 23, and 24 respectively. Examples 25-32 used an aqueous absorbingmedium with a concentration of 5 mol/L MEA to 2 mol/L MDEA and acirculation rate of 12-13 L/min.

Experimental Results for Examples 1-32

The plant experimental results and computer simulation results forExamples 1-32 are shown in the Table below. The following is a list ofexplanations for the different column headings in the Table: the ‘HeatDuty’ column refers to the external heat required to operate theregenerator; the ‘Lean Loading’ column refers to the loading of CO₂ inthe regenerated aqueous absorbing medium exiting the regenerator; the‘Rich Loading’ column refers to the loading of CO₂ in the rich aqueousabsorbing medium exiting the gas liquid contact apparatus; the ‘CO₂Production’ column refers to the recovered gaseous component; and the‘Steam Consumption’ column refers to the steam required to operate thereboiler.

General Information Relating to Examples 33-34

Data was obtained through computer simulations based on the Boundary Damcoal fired power plant in Estevan, Saskatchewan. The plant is designedto produce 4 tonnes of CO₂ per day from a flue gas obtained from a coalfired power plant. As such, the incoming gas contained both carbondioxide and sodium sulfide. Accordingly, the incoming gas was treated tolower the temperature and remove excess moisture and scrubbed to removethe sodium sulfide prior to entering the absorber. The incoming gasstream had the following composition: 14.86 mole % CO₂, 5.03 mol % O₂,64.93 mol % N₂, and 15.18 mol % H₂O. Furthermore, the incoming gasstream had the following conditions: inlet gas pressure 111.325 kPa,inlet gas temperature 36° C., and inlet gas flow 10 kg-mol/hr. InExamples 33-34, the steam supply pressure to the reboiler was between arange of about 230-475 kPa, the steam supply temperature to the reboilerwas between a range of about 125-150° C., and the reboiler temperaturewas about 121° C. The absorber efficiency was 90%. Examples 33-34 usedan aqueous absorbing medium with a concentration of 5 mol/L MEA to 2mol/L MDEA and a circulation rate of 12-13 L/min. The computersimulations were prepared using PROMAX™ software obtained from BryanResearch & Engineering, Bryan, Tex., USA.

Example 33

Example 33 was a computer simulation based on FIG. 9. The results forthis computer simulation are as follows: ‘Heat Duty’ is 35,831BTU/lb-mole; ‘Lean Loading’ is 0.3168 Mol CO₂/Mol aqueous absorbingmedium; ‘Rich Loading’ is 0.4662 Mol CO₂/Mol aqueous absorbing medium;‘CO₂ Production’ 0.910 tonne/day; and ‘Steam Consumption’ is 0.896 kg/kgCO₂.

Example 34

Example 34 was a computer simulation based on FIG. 17. The results forthis computer simulation are as follows: ‘Heat Duty’ is 14,716BTU/lb-mole; ‘Lean Loading’ is 0.3085 Mol CO₂/Mol aqueous absorbingmedium; ‘Rich Loading’ is 0.4687 Mol CO₂/Mol aqueous absorbing medium;‘CO₂ Production’ 0.913 tonne/day; and ‘Steam Consumption’ is 0.368 kg/kgCO₂.

Example 35

Example 35 was a computer simulation based on FIG. 25. Examples 35 usedan aqueous absorbing medium with a concentration of 5 mol/L MEA and acirculation rate of 14 L/min. The results for this computer simulationare as follows: ‘Heat Duty’ is 40,500 BTU/lb-mole; ‘Lean Loading’ is0.2609 Mol CO₂/Mol aqueous absorbing medium; ‘Rich Loading’ is 0.4766Mol CO₂/Mol aqueous absorbing medium; ‘CO₂ Production’ 0.912 tonne/day;and ‘Steam Consumption’ is 1.79 kg/kg CO₂.

Example 36

Example 36 was a computer simulation based on FIG. 25. Examples 36 usedan aqueous absorbing medium with a concentration of 5 mol/L MEA to 2mol/L MDEA and a circulation rate of 12-13 L/min. The results for thiscomputer simulation are as follows: ‘Heat Duty’ is 49,500 BTU/lb-mole;‘Lean Loading’ is 0.2622 Mol CO₂/Mol aqueous absorbing medium; ‘RichLoading’ is 0.4528 Mol CO₂/Mol aqueous absorbing medium; ‘CO₂Production’ 0.911 tonne/day; and ‘Steam Consumption’ is 1.21 kg/kg CO₂.

Examples 37-38

Examples 37-38 were computer simulations and plant experiments based onFIG. 26. The results are shown in the Table below. Although particularembodiments of one or more inventions have been described in detailherein with reference to the accompanying drawings, it is to beunderstood that each claimed invention is not limited to thoseparticular embodiments, and that various changes and modifications maybe effected therein by one skilled in the art without departing from thescope or spirit of any invention as defined in the appended claims.

Lean Loading Rich Loading (Mol CO₂/Mol (Mol CO₂/Mol aqueous aqueousSteam Heat Duty absorbing absorbing CO₂ Production Consumption Example(BTU/lb-mole) medium) medium) (tonne/day) (kg/kg CO₂) 1 72,890 0.25870.4588 0.847 1.80 2 70,114 0.2699 0.4819 0.917 1.75 3 55,888 0.27250.4828 0.910 1.40 4 63,297 0.2699 0.4819 0.917 1.58 5 60,768 0.27040.4821 0.916 1.52 6 60,367 0.2709 0.4811 0.909 1.51 7 60,047 0.26930.4816 0.919 1.50 8 57,860 0.2698 0.4806 0.912 1.45 9 57,426 0.26920.4816 0.919 1.44 10 57,400 0.2691 0.4816 0.919 1.44 11 55,982 0.27000.4819 0.917 1.40 12 57,222 0.2692 0.4804 0.914 1.43 13 55,777 0.27000.4807 0.912 1.40 14 62,188 0.2723 0.4828 0.910 1.56 15 49,224 0.26960.4805 0.912 1.20 16 48,432 0.2678 0.4798 0.917 1.18 17 32,422 0.26930.4803 0.913 0.79 18 52,768 0.2708 0.4809 0.909 1.32 19 55,766 0.26980.4805 0.912 1.40 20 55,763 0.2698 0.4805 0.912 1.40 21 50,485 0.26960.4805 0.912 1.26 22 21,041 0.2709 0.4816 0.912 0.526 23 18,372 0.27140.4826 0.914 0.460 24 16,812 0.2716 0.4754 0.913 0.421 25 49,030 0.28880.4604 0.912 1.23 26 42,713 0.2776 0.4626 0.910 1.07 27 39,511 0.28940.4607 0.911 0.988 28 39,575 0.2850 0.4563 0.912 0.990 29 5,778 0.27510.4606 0.913 0.145 30 12,663 0.2664 0.4596 0.909 0.317 31 12,126 0.28110.4594 0.910 0.303 32 7,354 0.2751 0.4606 0.913 0.184 37 Sim. 55,5900.2504 0.4837 0.57 1.30 Exp. 48,924 ± 5436 0.2270 0.5024 0.58 1.21 ±0.14 38 Sim. 43,733 0.2321 0.4222 0.53 1.04 Exp.  39231 ± 5117 0.18350.4252 0.58 0.98 ± 0.17

1. A method for recovering a gaseous component from an incoming gasstream, comprising: a) contacting the incoming gas stream with a leanaqueous absorbing medium to absorb at least a portion of the gaseouscomponent from the incoming gas stream to form a lean treated gas streamand a rich aqueous absorbing medium; b) desorbing at least a portion ofthe gaseous component from the rich aqueous absorbing medium at atemperature to form an overhead gas stream and a regenerated aqueousabsorbing medium; c) treating at least a portion of the overhead gasstream to recover a first condensate stream; d) using at least a portionof the first condensate stream to form a heated stream; e) recycling atleast a portion of the heated stream back to the desorbing step.
 2. Amethod according to claim 1, wherein heat is transferred from theincoming gas stream to the heated stream.
 3. A method according to anyone of claim 1 or 2, wherein heat is transferred from the overhead gasstream to the heated stream.
 4. A method according to any one of claims1 to 3, further comprising the steps of introducing steam to provideheat for the desorbing step and to form a steam condensate and flashingthe steam condensate to form a flashed steam and wherein heat istransferred from the flashed steam to the heated stream.
 5. A methodaccording to any one of claims 1 to 4, wherein heat is transferred fromthe regenerated aqueous absorbing medium to the heated stream.
 6. Amethod according to any one of claims 1 to 5, wherein the heated streamcomprises the first condensate stream.
 7. A method according to any oneof claims 1 to 5, wherein the heated stream comprises the rich aqueousabsorbing medium derived by delivering at least a portion of the firstcondensate stream to the contacting step so that at least a portion ofthe first condensate stream combines with the lean aqueous absorbingmedium to form the rich aqueous absorbing medium.
 8. A method accordingto any one of claims 1 to 5, further comprising the step of treating atleast a portion of the lean treated gas stream to recover a secondcondensate stream and wherein the heated stream comprises a mixedcondensate stream derived by combining at least a portion of the firstcondensate stream with at least a portion of the second condensatestream to form the mixed condensate stream.
 9. A method according toclaim 1, wherein the heated stream comprises a rich vapor stream and asemi-lean aqueous absorbing medium derived by delivering at least aportion of the first condensate stream to the contacting step so that atleast a portion of the first condensate stream combines with the leanaqueous absorbing medium to form the rich aqueous absorbing medium whichis subsequently flashed to form the rich vapor stream and the semi-leanaqueous absorbing medium.
 10. A method according to claim 9, whereinheat is transferred from the incoming gas stream to at least one of therich aqueous absorbing medium or the semi-lean aqueous absorbing medium.11. A method according to any one of 9 or 10, wherein heat istransferred from the overhead gas stream to at least one of the richaqueous absorbing medium or the semi-lean aqueous absorbing medium. 12.A method according to any one of claims 9 to 11, further comprising thesteps of introducing steam to provide heat for the desorbing step and toform a steam condensate and flashing the steam condensate to form aflashed steam and wherein heat is transferred from the flashed steam toat least one of the rich aqueous absorbing medium or the semi-leanaqueous absorbing medium.
 13. A method according to any one of claims 9to 12, wherein heat is transferred from the regenerated aqueousabsorbing medium to at least one of the rich aqueous absorbing medium orthe semi-lean aqueous absorbing medium.
 14. A method according to claim1, wherein the heated stream comprises a first rich aqueous absorbingmedium portion and a second rich aqueous absorbing medium portionderived by delivering at least a portion of the first condensate streamto the contacting step so that at least a portion of the firstcondensate stream combines with the lean aqueous absorbing medium toform the rich aqueous absorbing medium which is subsequently split intothe first rich aqueous medium portion and the second rich aqueousabsorbing medium portion.
 15. A method according to claim 14, whereinheat is transferred from the incoming gas stream to at least one of therich aqueous absorbing medium, the first rich aqueous absorbing mediumportion or the second rich absorbing medium portion.
 16. A methodaccording to any one of 14 or 15, wherein heat is transferred from theoverhead gas stream to at least one of the rich aqueous absorbingmedium, the first rich aqueous absorbing medium portion or the secondrich absorbing medium portion.
 17. A method according to any one ofclaims 14 to 16, further comprising the steps of introducing steam toprovide heat for the desorbing step and to form a steam condensate andflashing the steam condensate to form a flashed steam and wherein heatis transferred from the flashed steam to at least one of the richaqueous absorbing medium, the first rich aqueous absorbing mediumportion or the second rich absorbing medium portion.
 18. A methodaccording to any one of claims 14 to 17, wherein heat is transferredfrom the regenerated aqueous absorbing medium to at least one of therich aqueous absorbing medium, the first rich aqueous absorbing mediumportion or the second rich absorbing medium portion.
 19. A methodaccording to claim 1, further comprising the step of treating at least aportion of the lean treated gas stream to recover a second condensatestream and wherein the heated stream comprises a first mixed condensatestream portion and a second mixed condensate stream portion derived bycombining at least a portion of the first condensate stream with atleast a portion of the second condensate stream to form the mixedcondensate stream and subsequently splitting the mixed condensate streamto form the first mixed condensate stream portion and the second mixedcondensate stream portion.
 20. A method according to claim 19, whereinheat is transferred from the incoming gas stream to at least one of themixed condensate stream, the first mixed condensate stream portion orthe second mixed condensate stream portion.
 21. A method according toany one of 19 or 20, wherein heat is transferred from the overhead gasstream to at least one of the mixed condensate stream, the first mixedcondensate stream portion or the second mixed condensate stream portion.22. A method according to any one of claims 19 to 21, further comprisingthe steps of introducing steam to provide heat for the desorbing stepand to form a steam condensate and flashing the steam condensate to forma flashed steam and wherein heat is transferred from the flashed steamto at least one of the mixed condensate stream, the first mixedcondensate stream portion or the second mixed condensate stream portion.23. A method according to any one of claims 19 to 22, wherein heat istransferred from the regenerated aqueous absorbing medium to at leastone of the mixed condensate stream, the first mixed condensate streamportion or the second mixed condensate stream portion.
 24. A methodaccording to any one of claims 1 to 23, further comprising the step ofrecycling the regenerated aqueous absorbing medium back to thecontacting step.
 25. A method according to any one of claims 1 to 24,wherein the incoming gas stream is a combustion exhaust gas.
 26. Amethod according to any one of claims 1 to 25, wherein the gaseouscomponent is carbon dioxide.
 27. A method according to claim any one ofclaims 1 to 26, wherein the lean aqueous absorbing medium comprisesmonoethanolamine, methyldiethanolamine and a suitable solvent.
 28. Amethod according to claim 27, wherein the molar ratio ofmonoethanolamine to methydiethanolamine is between about 1.5:1 to about4:1 and the total molarity of monoethanolamine and methyldiethanolamineis between about 3 moles/liter to about 9 moles/liter.
 29. A methodaccording to claim 28, wherein the molar ratio of monoethanolamine tomethydiethanolamine is about 2.5:1 and the total molarity ofmonoethanolamine and methyldiethanolamine is about 7 moles/liter.
 30. Anaqueous absorbing medium for removing a gaseous component from anincoming gas stream, the aqueous absorbing medium comprisingmonoethanolamine, methyldiethanolamine and a suitable solvent, the molarratio of monoethanolamine to methydiethanolamine is between about 1.5:1to about 4:1 and the total molarity of monoethanolamine andmethyldiethanolamine is between about 3 moles/liter to about 9moles/liter.
 31. An aqueous absorbing medium according to claim 30,wherein the molar ratio of monoethanolamine to methydiethanolamine isabout 2.5:1 and the total molarity of monoethanolamine andmethydiethanolamine is about 7 moles/liter.
 32. A method for producingan aqueous absorbing medium, comprising: a) providing monoethanolamine;b) providing methyldiethanolamine; c) providing a suitable solvent; d)combining the monoethanolamine, the methyldiethanolamine and the solventto form the aqueous absorbing medium; and wherein the molar ratio ofmonoethanolamine to methydiethanolamine is between about 1.5:1 to about4:1 and the total molarity of monoethanolamine and methydiethanolamineis between about 3 moles/liter to about 9 moles/liter.
 33. A methodaccording to claim 32, wherein the molar ratio of monoethanolamine tomethydiethanolamine is about 2.5:1 and the total molarity ofmonoethanolamine and methydiethanolamine is about 7 moles/liter.
 34. Amethod for removing a gaseous component from an incoming gas stream,comprising contacting the incoming gas stream with an aqueous absorbingmedium comprising monoethanolamine, methyldiethanolamine and a suitablesolvent, the molar ratio of monoethanolamine to methydiethanolamine isbetween about 1.5:1 to about 4:1 and the total molarity ofmonoethanolamine and methyldiethanolamine is between about 3 moles/literto about 9 moles/liter.
 35. A method according to claim 33, wherein themolar ratio of monoethanolamine to methydiethanolamine is about 2.5:1and the total molarity of monoethanolamine and methyldiethanolamine isabout 7 moles/liter.